Gel chromatography: Introduction, Principle & Classifications

Introduction:

• Gel chromatography, also known as gel filtration chromatography, gel permeation chromatography, or size exclusion chromatography (SEC), is a chromatographic technique that separates molecules based on their size.

• It's commonly used in the pharmaceutical industry to analyze and purify biomolecules such as proteins, peptides, nucleic acids, and polysaccharides.

• In gel chromatography, a column is packed with porous beads, which are made from a variety of materials such as agarose, dextran, or polyacrylamide.
  

• When a mixture of molecules is passed through this column, smaller molecules enter the pores of the beads, whereas larger molecules are excluded.

• Due to this selective permeation, larger molecules elute from the column before smaller ones.

Principle:

• Gel chromatography, also known as size exclusion chromatography (SEC), separates molecules based on their size or hydrodynamic volume as they navigate a column packed with porous beads.

Here's the colored diagram illustrating the principle of Gel Chromatography:

• When a solution of molecules is introduced into this column:

  1. Large Molecules: These are too big to enter the pores and travel around the beads, resulting in a quicker elution through the column.

  2. Intermediate Molecules: These can partially enter some of the pores, leading to a somewhat slower passage than the larger molecules.

  3. Small Molecules: These permeate most or all of the pores, making their journey the longest and eluting last.

• It's crucial to understand that the separation isn't based on the intrinsic size of the molecule, but on the hydrodynamic volume or shape it adopts in solution.

Classification of Gel Chromatography:

Here's a colored diagram illustrating the classification of Gel Chromatography

Based on the type of materials and intended use, gel chromatography can be classified into:

1. Gel Filtration Chromatography (GFC):

• Typically used for aqueous samples and employs hydrophilic gels like dextran or agarose.

• It's mostly utilized in protein purification and analysis.

2. Gel Permeation Chromatography (GPC):

• Used primarily for the analysis of synthetic polymers in organic solvents.

• Polystyrene or polydivinylbenzene beads are often employed.

3. Based on Pore Size:

1. Micro-Porous: Suitable for separating low molecular weight compounds.

2. Meso-Porous: Ideal for medium molecular weight compounds.

3. Macro-Porous: Used for high molecular weight compounds.

4. Based on Usage:

1. Analytical Gel Chromatography: Used to analyze molecular weight, size, and sample purity.

2. Preparative Gel Chromatography: Aimed at purifying and collecting significant quantities of specific molecules.